With non of these "methods" I ever had success. DroidWall is not preventing update as well as other Firewalls, at least in my experience, I tried with every update another one.
This time nothing done, got the update, plugged to PC, KFU, 10 sec later rooted again. Not worth the effort for me playing around with another hint not working in the end.

Droidwall seemed to work ok to prevent me from getting 6.3 but I neglected to re-enable it after some troubleshooting last week, so I got 6.3.1.

However, it did not completely unroot me - I was still able to use adb in root mode, which let me put back /system/xbin/su, making me fully rooted again in a few seconds. If this keeps up I'm fine with it.

Yes, with the 6.3 update, I also forgot to re-enable DroidWall and it updated me, but so far, knock wood, with that file that I removed I have not received the 6.3.1 update.
How do you "put back /system/xbin/su" in case I have to do that....do you need Linux installed on your PC? I'm using Win 7, 32 bit and I had to re-root by going through the FireFireFire steps again with 6.3.

But like I say so far so good with the removal of that one file - no update to 6.3.1.

I have to reiterate that it is not really necessary to be rooted at all; you can use Go Launcher EX and Rotating Wallpaper app and sideload nearly all apps without rooting. There's a Live Wallpaper you can use to rotate wallpaper also.

Yes, with the 6.3
How do you "put back /system/xbin/su" in case I have to do that....do you need Linux installed on your PC? I'm using Win 7, 32 bit and I had to re-root by going through the FireFireFire steps again with 6.3.

I don't think it needs to be linux (I have been using linux in a virtualbox virtual machine because for some reason I couldn't get adb working on win7 on my laptop, although it works on my win7 desktop), but you do need to have a working adb setup (which you should if you already rooted).

First of all, what I had done on a rooted Fire in preparation for my 'preserve root' attempt:

adb shell (you can also use the 'terminal' app if you have it)
$ su (skip this if you already have a # prompt)
# mkdir /data/mydir
# cat /system/xbin/su > /data/mydir/su
# echo "service.root.amazon.allow=1" > /data/local.prop

It is also helpful to stash busybox in /data/mydir if you have it, since it will give you helpful unix commands to work with.

Now, post-update, to get su back into place:

adb root
adb remount
adb shell

If you still have adb root access at this point you will have a # prompt. If you have a $ prompt the rest will not work. The /data/local.prop trick above seems to have preserved adb root access for me in both 6.3 and 6.3.1 updates.

Thanks for taking the time to post those instructions.
Where do I type abd shell and all those lines? Do I do this on the KF itself? I need to install a terminal app, don't I?

This reminds me of working with my Zaurus. It was so funny to go to the forums and see posts of lines and lines of code which a poster said had to be typed into the terminal and then there was usually a followup posting which said, just click on the such and such icon and type "root" and it did the same thing.

If I knew WHERE to type those lines I may try it if I have to, although the FireFireFire method has worked for me the last couple of times with minimal problems and it installs TWRP and the Google Apps.

Thanks for taking the time to post those instructions.
Where do I type abd shell and all those lines? Do I do this on the KF itself? I need to install a terminal app, don't I?

the adb commands would be done in a windows cmd window or a linux terminal. I was not specific on those because that detail is covered under the umbrella of getting adb working - if you used the kindle fire utility to root, adb should be in the directory where you put kfu and you may need to cd there and use .\adb (windows) or ./adb (linux) instead of just 'adb'; if you have installed the android sdk then it's somewhere in the android sdk directory structure.

The commands indicated by a $ or # prompt would normally be done in that same window after starting a shell via adb. But in some cases (everything other than the post-upgrade step of copying su into /system/xbin) you can use the terminal app (get from the google market) on your Fire to do the same thing. It is easier to type on your pc than on the Fire screen though!

I don't think it needs to be linux (I have been using linux in a virtualbox virtual machine because for some reason I couldn't get adb working on win7 on my laptop, although it works on my win7 desktop), but you do need to have a working adb setup (which you should if you already rooted).

First of all, what I had done on a rooted Fire in preparation for my 'preserve root' attempt:

adb shell (you can also use the 'terminal' app if you have it)
$ su (skip this if you already have a # prompt)
# mkdir /data/mydir
# cat /system/xbin/su > /data/mydir/su
# echo "service.root.amazon.allow=1" > /data/local.prop

It is also helpful to stash busybox in /data/mydir if you have it, since it will give you helpful unix commands to work with.

Now, post-update, to get su back into place:

adb root
adb remount
adb shell

If you still have adb root access at this point you will have a # prompt. If you have a $ prompt the rest will not work. The /data/local.prop trick above seems to have preserved adb root access for me in both 6.3 and 6.3.1 updates.

the adb commands would be done in a windows cmd window or a linux terminal. I was not specific on those because that detail is covered under the umbrella of getting adb working - if you used the kindle fire utility to root, adb should be in the directory where you put kfu and you may need to cd there and use .\adb (windows) or ./adb (linux) instead of just 'adb'; if you have installed the android sdk then it's somewhere in the android sdk directory structure.

The commands indicated by a $ or # prompt would normally be done in that same window after starting a shell via adb. But in some cases (everything other than the post-upgrade step of copying su into /system/xbin) you can use the terminal app (get from the google market) on your Fire to do the same thing. It is easier to type on your pc than on the Fire screen though!

Okay, I DO have adb installed in a folder on my C Drive on my PC and just opened a command window in that folder and was able to get a "daemon" running when I ran adb shell but I think I will stick to the easier FireFireFire routine.
Glad to have this in my back pocket in case I run into difficulties with FireFire Fire in the future so thanks for the instructions.

Yeah, it's definitely not a process for everyone, but since I do unix for a living, it's comfortable to me and I am less concerned about it screwing something up than some black box written by someone else :-)